Apparatus for extruding cellulose fibers

ABSTRACT

An apparatus is disclosed for extruding cellulose fibers. The apparatus includes a first member, a second member and a third member all secured together. Multiple nozzles extend outward from the first member and each is designed to direct an aqueous cellulose solution therethrough. As the aqueous solution is extruded, it is accentuated and accelerated by pressurized gas flowing through the first member and the second member and out through first openings formed in the third member. The pressurized gas at least partially surrounds each nozzle and shelters the molten filaments extruded therefrom. The third member also has multiple second openings formed therethrough which are also connected to a source of pressurized gas. The pressurized gas streams exiting each of the second openings function to keep each of the molten filaments from contacting an adjacent molten filament.

FIELD OF THE INVENTION

This invention relates to an apparatus for extruding cellulose fibers.

BACKGROUND OF THE INVENTION

Currently, there are several different methods for extruding an aqueoussolution containing cellulose and a water soluble solvent into cellulosefibers. Each of these methods utilizes special equipment to heat theaqueous solution and extrude it through a die block assembly. The dieblock assembly can include various components for directing anddistributing the aqueous solution and pressurized gas through aplurality of nozzles to form a plurality of molten filaments. Theaqueous solution is usually extruded in a downward direction such thatthe pressurized gas and gravity will cause the aqueous solution toattenuate into a plurality of molten filaments. The molten filaments arethen contacted with a liquid which causes a major portion of the solventto solvate into the liquid solution and thus allows the molten filamentsto coagulate into solid cellulose fibers. These solid cellulose fibersare then collected on a moving surface, such as a porous conveyor beltor rotatable drum and form a non-woven web.

Up until now, no one has been able to design and construct an apparatusor process which will allow cellulose fibers having a diameter of lessthan about 15 microns to be extruded and formed at a throughput thatwould make such a process economically feasible. In addition, no one hasbeen able to design and construct a spinnerette that extrudes 20 or moremolten filaments per linear centimeter at a throughput of greater than0.1 grams/hole/minute at a production speed of up to about 750 metersper minute. Furthermore, no one has been able extrude an aqueoussolution containing cellulose and a solvent at back pressures of morethan 20 bar without damaging the spinnerette. Still further, no one todate has been able to extrude and form very fine cellulose fibers havinga diameter of less than 5 micron at a throughput of greater than 0.5grams/hole/minute at a production speed of up to about 750 meters perminute. Lastly, no one to date has been able to form a non-woven webconstructed from such cellulose fibers which has a basis weight of lessthan about 1 gram per square meter at a production rate of more thanabout 30 meters per minute.

Now an apparatus has been invented which will allow one to extrude andform cellulose fibers each having a diameter of less than about 15microns at a throughput of greater than about 0.1 grams/hole/minute. Theapparatus is also capable of forming very fine cellulose fibers eachhaving a diameter of less than about 5 microns at a throughput ofgreater than about 0.5 grams/hole/minute. Furthermore, the apparatusproduces cellulose fibers having unique characteristics that can becollected to form a non-woven web.

SUMMARY OF THE INVENTION

Briefly, this invention relates to an apparatus for extruding cellulosefibers. The apparatus includes a first member secured to a dope deliverymechanism. The first member has multiple nozzles arranged in rows. Eachof the nozzles has an inside diameter through which an aqueous solutionof cellulose and a solvent can be extruded. Each of the nozzles also hasat least one other passage formed therein through which a pressurizedgas can be routed. The apparatus also includes a second member securedto the first member. The second member has multiple corridors formedtherethrough which are connected to the passage formed in the firstmember, and multiple openings formed therein through which the multiplenozzles can pass. The apparatus further includes a third member securedto the second member. The third member has multiple first openingsformed therethrough. Each of the multiple first openings is sized topermit one of the multiple nozzles to pass therethrough. Each of thefirst openings being connected to the pressurized gas corridors formedin the second member. Each of the first openings is capable of emittingpressurized gas therethrough such that the pressurized gas at leastpartially surrounds the aqueous solution extruded from each of thenozzles. The third member also has multiple second openings formedtherethrough which are connected to the pressurized gas corridors formedin the second member. Each of the second openings is positioned adjacentto one of the nozzles, in each of the rows, and each of the secondopenings has an opening through which the pressurized gas can beemitted.

The general object of this invention is to provide an apparatus capableof extruding cellulose fibers having a diameter of less than about 15microns at a throughput of greater than 0.1 grams/hole/minute at aproduction speed of up to about 750 meters per minute. A more specificobject of this invention is to provide an apparatus capable of extrudingvery fine cellulose fibers having a diameter of less than about 5microns at a throughput of greater than 0.5 grams/hole/minute at aproduction speed of up to about 750 meters per minute.

Another object of this invention is to provide an apparatus forextruding cellulose fibers having a circular cross-sectionalconfiguration and a diameter of about 5 microns or less.

A further object of this invention is to provide an apparatus forextruding very fine cellulose fibers having a diameter of less thanabout 3 microns.

Still another object of this invention is to provide an apparatus forextruding cellulose fibers which includes an array of nozzles which arecapable of extruding an aqueous solution of cellulose and a watersoluble solvent along with pressurized gas such that an attenuatedmolten filament will not adhere to an adjacent molten filament.

Still further, an object of this invention is to provide an apparatusfor extruding cellulose fibers in an economical and efficient manner.

Other objects and advantages of the present invention will become moreapparent to those skilled in the art in view of the followingdescription and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a process of forming cellulose fibers.

FIG. 2 is a cross-sectional view of a die block assembly showingmultiple first and second nozzles.

FIG. 3 is an end view of a nozzle.

FIG. 4 is an end view of a second nozzle.

FIG. 5 is a partial exploded view of a portion of the spinnerette bodyshown within the area labeled A.

FIG. 6 is an enlarged, partial cross-sectional view of a second nozzlehaving a constant inside diameter.

FIG. 7 is an enlarged, partial cross-sectional view of a second nozzlehaving a venturi.

FIG. 8 is an end view of an alternative design for the first opening.

FIG. 9 is an end view of still another embodiment for the first opening.

FIG. 10 is an end view of a further embodiment for the first opening.

FIG. 11 is an end view of still another embodiment for the firstopening.

FIG. 12 is an end view of still another embodiment for the firstopening.

FIG. 13 is a plane view of an array of first and second nozzles formedin an exterior plate.

FIG. 14 is a plane view of an alternative array of first and secondnozzles formed in an exterior plate.

FIG. 15 is a plane view of an array wherein each nozzle is surrounded bythree of the second openings.

FIG. 16 is a plane view of an array wherein each nozzle is surrounded byfour of the second openings.

FIG. 17 is a plane view of an array wherein each nozzle is surrounded bysix of the second openings.

FIG. 18 is a plane view of an array wherein each nozzle is surrounded byeight of the second openings.

FIG. 19 is an enlarged cross sectional view of a nozzle showing a moltenfilament being extruded therefrom.

FIG. 20 is a plane view of a coagulated cellulose fiber.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a process 10 of forming cellulose fibers 12 whichcan be formed into a non-woven web 14 is shown. The process 10 includesthe steps of combining and dissolving cellulose 16 and a solvent 18 toform an aqueous solution 20. The aqueous solution 20 is commonlyreferred to as dope in the industry. The type of raw cellulosic materialused can vary. Cellulose is a complex carbohydrate C₆H₁₀O₅ that iscomposed of glucose units which form the main constituent of the cellwall in most plants. The cellulosic material may be bleached orunbleached wood pulp which can be made by various processes of whichkraft, pre-hydrolyzed kraft, and sulfite would be exemplary. Many othercellulosic raw materials, including but not limited to: purified cottonlinters, plants, grasses, etc. can also be used separately or incombination with wood pulp. The cellulose 16 can be wood pulp from anyof a number of commercially available dissolving or non-dissolving gradepulps. Examples of some sources of wood pulp include: The WeyerhaeuserCompany, International Paper Company, Sappi Saiccor sulfite pulp, andpre-hydrolyzed kraft pulp from International Paper Company. In addition,the wood pulp can be a high hemi-cellulose with a low degree ofpolymerization pulp. The cellulosic material can be chopped or shreddedinto a fine fluff to promote forming an aqueous solution 20 with thesolvent 18.

The solvent 18 is desirably a water soluble solvent. For example, thesolvent 18 can be an amine oxide, desirably a tertiary amine N-oxidecontaining a non-solvent for the cellulose, such as water.Representative examples of amine oxide solvents useful in the practiceof this invention are set forth in U.S. Pat. No. 5,409,532, issued toAstegger et al. The desired solvent is N-methyl-morpholine-N-oxide(NMMO). Other representative examples of solvents includedimethylsulfoxide (DMSO), dimethylacetamide (DMAC), dimethylforamide(DMF) and caprolactan derivatives. The pulp can be dissolved in an amineoxide solvent by any art recognized means such as set forth in U.S. Pat.No. 4,246,221, issued to McCorsley, III; U.S. Pat. No. 5,330,567, issuedto Zikeli et al. and U.S. Pat. No. 5,534,113, issued to Quigley et al.Still other solvents that may be used in this invention include dilutecaustic soda, phosphoric acid, a mixture of liquid ammonia/ammoniathiocynate and others. Still another way of making an aqueous solutionof the cellulose is described in U.S. Pat. No. 6,306,334 issued to Luoet al.

The aqueous solution 20 is then heated in a heater 22 or by some othertype of heating mechanism to a predetermined elevated temperature. Theaqueous solution 20 can be heated to a temperature ranging from betweenabout 80° C. to about 140° C. Desirably, the aqueous solution 20 isheated to a temperature of at least 100° C. More desirably, the aqueoussolution 20 is heated to a temperature of at least about 110° C. Mostdesirably, the aqueous solution 20 is heated to a temperature of atleast about 120° C.

The aqueous solution 20 of the cellulose 16 and solvent 18 can be madein a known manner, for example, as taught in U.S. Pat. No. 4,246,221,issued to McCorsley, III which is incorporated by reference and made apart hereof. In U.S. Pat. No. 4,246,221, the cellulose is wet in anon-solvent mixture of about 40% NMMO and 60% water. The ratio ofcellulose to wet NMMO is about 1:5.1 by weight. The mixture is mixed ina double arm sigma blade mixer for about 1.3 hours under vacuum at about120° C. until sufficient water has been distilled off to leave about12%-18% based on NMMO so that a cellulose solution is formed. Theresulting dope should contain from about 8% to about 15% cellulose.

The heated aqueous solution 20 is then directed to a dope deliverymechanism 24, for example an extruder, where it is routed through a dieblock/spinnerette assembly 26. The die block/spinnerette assembly 26 canbe directly secured to the dope delivery mechanism 24 or it can bespaced apart from the dope delivery mechanism 24.

It should be noted that even though the preparation of the aqueoussolution 20, consisting of cellulose 16 and a water soluble solvent 18,such as aqueous NMMO, is known to those skilled in the art, theapparatus and method of spinning the heated aqueous solution 20 intocellulose fibers 12 is very unique. Up until now, no one has been ableto form cellulose fibers 12 each having a diameter of less than about 15microns at a throughput of greater than 0.1 grams/hole/minute at aproduction speed of up to about 750 meters per minute. In addition, noone has been able to form very fine cellulose fibers 12 each having adiameter of less than about 5 microns at a throughput of greater than0.5 grams/hole/minute at a production speed of up to about 750 metersper minute.

Referring now to FIG. 2, the die block/spinnerette assembly 26 includesa die block 28 having a first conduit 30 formed therein through whichthe heated aqueous solution 20 is routed. The die block 28 also has atleast one second conduit 32 formed therein. In FIG. 2, a pair of secondconduits 32 is shown in a spaced apart configuration. Each of the secondconduits 32 is sized and configured to route or direct a pressurized gas34 therethrough. Desirably, the pressurized gas 34 is air.

Those skilled in the art should understand that two, three, four or moresecond conduits 32 can be utilized. For better distribution of thepressurized gas 34, multiple spaced apart, second conduits 32 can beutilized.

The pressurized gas 34 is normally heated to a predetermined elevatedtemperature. The pressurized gas 34 can be heated to a temperatureranging from between about 100° C. to about 160° C. Desirably, thepressurized gas 34 is heated to a temperature ranging from between about110° C. to about 160° C. More desirably, the pressurized gas 34 isheated to a temperature ranging from between about 120° C. to about 160°C. Most desirably, the pressurized gas 34 is heated to a temperature ofabout 120° C. The pressurized gas 34 should have a velocity of at leastabout 45 meters per second (m/sec.). Desirably, the pressurized gas 34should have a velocity ranging from between about 45 m/sec. to about 500m/sec. More desirably, the pressurized gas 34 should have a velocityranging from between about 50 m/sec. to about 450 m/sec.

It should be evident to one skilled in the art that the cross-sectionalarea, the internal shape and the internal configuration of each of theconduits 32 can vary. The internal diameter of each of the conduits 32,the material from which each of the conduits 32 are formed of, the backpressure on the pressurized gas 34, the temperature of the pressurizedgas 34, the as well as other factors, will influence the velocity of thepressurized gas 34.

The die block/spinnerette assembly 26 also includes a filter block 36which is secured to the die block 28. The filter block 36 has at leasttwo separate passageways 38 and 40 formed therethrough. The passageway38 is sized and configured to match up and align with the first conduit30 so that the heated aqueous solution 20 can be routed through thefilter block 36. The other passageways 40, of which two are shown, aresized and configured to match up and align with the two second conduits32 so that the pressurized gas 34 can be routed through the filter block36. It should be understood that the size and shape of the passageways38 and 40 do not have to be identical to the size and shape of the firstand second conduits, 30 and 32 respectively. However, the number ofpassageways 40 should be equal to the number of conduits 32 and eachpassageway 40 should be aligned with one of the conduits 32.

The filter block 36 serves to filter particulate matter, such asnon-dissolved pulp, solution grit, etc. from the aqueous solution 20.

Referring to FIGS. 2 and 3, the die block/spinnerette assembly 26further includes a first member 42 which can be a spinnerette. The firstmember 42 is secured to the filter block 36. The filter block 36 issandwiched between the die block 28 and the first member or spinnerette42. The first member 42 has multiple nozzles 44 arranged in rows and/orcolumns or in some other desired pattern. Each of the nozzles 44 can beformed from a metal such as steel, stainless steel, a metal alloy, aferrous metal, etc. Desirably, each of the nozzles 44 is formed fromstainless steel. Each of the nozzles 44 is shown as an elongated, hollowtube 46. By “tube” it is meant a hollow cylinder, especially one thatconveys fluid or functions as a passage. Each of the hollow cylindricaltubes 46 has a longitudinal central axis X-X and a uniquely shapedcross-section. Desirably, the cross-section is circular but almost anygeometrical cross-section can be utilized. The cross-section should beconstant. Each of the hollow cylindrical tubes 46 has an inside diameterd and an outside diameter d₁. The inside diameter d can range frombetween about 0.125 millimeters (mm) to about 1.25 mm. The outsidediameter d₁ should be at least about 0.5 mm. Desirably, the outsidediameter d₁ of each of the hollow cylindrical tubes 46 can range frombetween about 0.5 mm to about 2.5 mm.

The heated aqueous solution 20 is extruded through the inside diameter dof each of the hollow cylindrical tubes 46. The back pressure on theheated aqueous solution 20 present in the passageway 38 of the filterblock 36 or in each of the hollow cylindrical tubes 46 should be equalto or exceeds about 5 bar. By “bar” it is meant a unit of pressure equalto one million (10⁶) dynes per square centimeter. Desirably, the backpressure on the heated aqueous solution 20 present in each of the hollowcylindrical tubes 46 can range from between about 20 bar to about 200bar. More desirably, the back pressure on the heated aqueous solution 20present in each of the hollow cylindrical tubes 46 can range frombetween about 25 bar to about 150 bar. Even more desirably, the backpressure on the heated aqueous solution 20 present in each of the hollowcylindrical tubes 46 can range from between about 30 bar to about 100bar.

The first member or spinnerette 42 also has at least one other passage48 formed therein. In FIG. 2, two spaced apart passages 48 are depicted,each of which is sized and configured to align with one of the twopassageways 40 formed through the filter block 36. The passages 48 areconnected to an enlarged chamber 50 formed on one surface of the firstmember or spinnerette 42. The enlarged chamber 50 can be centrallylocated about the longitudinal central axis X-X of each of the hollowcylindrical tubes 46. The enlarged chamber 50 is spaced away from andaligned opposite to the surface of the first member or spinnerette 42that is secured to the filter block 36. The size, depth and shape of theenlarged chamber 50 can vary. Desirably, the enlarged chamber 50 has acircular shape with a depth of at least 0.1 inches. More desirably, theenlarged chamber 50 has a circular shape with a depth of at least 0.2inches. The passages 48 function to direct the pressurized gas 34 fromthe passageways 40 to the enlarged chamber 50 of the spinnerette 42.

It should be understood that since the number of passageways 40 formedin the filer block 36 can vary, the number of passages 48 formed in thefirst member or spinnerette 42 can also vary. Desirably, there will bean equal number of passages 48 formed in the first member or spinnerette42 to correspond and align with the number of passageways 40 formed inthe filter block 36. As stated above, better distribution of thepressurized gas 34 may be possible when a greater number of passageways40 and passages 48 are utilized. For example, twelve passageways 40 canbe formed in the filter block 36 and each can be aligned with one of thetwelve passages 48 formed in the first member or spinnerette 42. Each ofthe twelve passageways 40, as well as each of the twelve passages 48,can be spaced approximately 30 degrees apart from an adjacent passageway40 or passage 48 respectively, when viewing the filter block 36 and thefirst member or spinnerette 42 from one end. Better distribution of thepressurized gas 34 correlates with more uniformly formed cellulosefibers 12.

Still referring to FIG. 2, the die block/spinnerette assembly 26 furtherincludes a second member in the form of a gas distribution plate 52. Thesecond member is secured to the first member or spinnerette 42. Thefirst member or spinnerette 42 is sandwiched between the filter block 36and the second member or gas distribution plate 52. The second member orgas distribution plate 52 has multiple corridors 54 formed therein. Thesecond member or gas distribution plate 52 also has a chamber 56 spacedaway from and aligned opposite to the surface of the second member orgas distribution plate 52 that is secured to the first member orspinnerette 42. The corridors 54 connect the enlarged chamber 50 to thechamber 56. The chamber 56 can be centrally located about thelongitudinal central axis X-X of each of the hollow cylindrical tubes46. The size, depth and shape of the chamber 56 can vary. The corridors54 function to route the pressurized gas 34 through the second member orgas distribution plate 52. The second member or gas distribution plate52 also has multiple openings 58 formed therethrough which are separateand distinct from the corridors 54. Each of the multiple openings 58 issized to permit one of the multiple nozzles 44, in the form of theelongated, hollow cylindrical tubes 46, to pass therethrough. Desirably,each of the multiple openings 58 has a circular cross-section with adiameter d₂ that is larger than the outside diameter d₁ of each of thehollow cylindrical tubes 46. In other words, the outside diameter d₁ ofeach of the hollow cylindrical tubes 46 does not form a snug or aninterference fit with the inside diameter d₂ of each of the multipleopenings 56.

It should be understood that additional smaller holes or passages canalso be formed in the second member or gas distribution plate 52 toallow pressurized gas to pass therethrough.

Referring again to FIGS. 2 and 3, the die block/spinnerette assembly 26includes a third member in the form of an exterior plate 60. The thirdmember or exterior plate 60 is secured to the second member or gasdistribution plate 52. The second member or gas distribution plate 52 issandwiched between the first member or spinnerette 42 and the thirdmember or exterior plate 60. The third member or exterior plate 60 hasmultiple first openings 62 formed therethrough. Each of the multiplefirst openings 62 is sized to freely permit one of the multiple nozzles44, in the form of an elongated, hollow cylindrical tube 46, to passtherethrough, see FIG. 3. Each of the hollow cylindrical tubes 46 canextend outward or downward beyond the third member or exterior plate 60.The distance the free end of each of the hollow cylindrical tubes 46extends beyond the exterior plate 60 can vary. Alternatively, each ofthe hollow cylindrical tubes 46 can stop short of the third member orexterior plate 60.

Each of the nozzles 44 has a first openings 62 formed adjacent thereto.Desirably, each of the first openings 62 is concentrically aligned abouteach of the nozzles 44. Each of the multiple first openings 62 can havea uniquely shaped cross-section with an inside diameter d₂, see FIG. 3.Desirably, each of the multiple first openings 62 has a circularcross-section. The inside diameter d₂ of each of the first openings 62can vary. Desirably, each of the first openings 62 has the same insidediameter d₂. More desirably, the inside diameter d₂ of each of the firstopenings 62 is at least 7.5 mm. Even more desirably, the inside diameterd₂ of each of the first openings 62 is at least 10 mm. Most desirably,the inside diameter d₂ of each of the first openings 62 is at least 12mm.

The inside diameter d₂ of each of the first openings 62 should begreater than the outside diameter d₁ of each of the hollow cylindricaltubes 46. Each of the first openings 62 is connected to the chamber 56formed in the second member or gas distribution plate 52. Each of thefirst openings 62 is capable of emitting pressurized gas 34 therethroughsuch that the pressurized gas 34 at least partially surrounds the heatedaqueous solution 20 extruded from each of the nozzles 44. Desirably,each of the first openings 62 completely surrounds the heated aqueoussolution 20 extruded from each of the nozzles 44 and this pressurizedair shrouds or forms a curtain around the heated aqueous solution 20extruded from each of the nozzles 44.

Referring to FIGS. 2 and 4, the third member or exterior plate 60 alsohas multiple second openings 64 formed therethrough which are connectedto the chamber 56 formed in the second member or gas distribution plate52. Each of the multiple second openings 64 has a uniquely shapedcross-section through which the pressurized gas 34 can be emitted.Desirably, each of the multiple second openings 64 has a circularcross-section. Each of the multiple second openings 64 has an insidediameter d₃. Desirably, the inside diameter d₃ is of a single dimension.The inside diameter d₃ of each of the multiple second openings 64 canvary. Desirably, the inside diameter d₃ of each of the multiple secondopenings 64 is of the same dimension. More desirably, the insidediameter d₃ of each of the second openings 64 is equal to the insidediameter d₂ of each of the first openings 62. More desirably, the insidediameter d₃ of each of the second openings 64 is at least 0.75 mm. Evenmore desirably, the inside diameter d₃ of each of the second openings 64is at least 1.0 mm. Most desirably, the inside diameter d₃ of each ofthe second openings 64 is at least 1.2 mm.

Each of the second openings 64 can be positioned adjacent to one of the30 first openings 62. Each of the first and second openings, 62 and 64is aligned parallel to one another. Alternatively, two or more of eachof the second openings 64 can be positioned adjacent to one of the firstopenings 62. In some embodiments, three (3) to eight (8) of the secondopenings 64 can be positioned adjacent to one of the first openings 62.Still further, each of the second 35 openings 64 can also be positionedadjacent to one of the nozzles 44 in each of the rows or in each of anadjacent row. Many different patterns or arrays can be utilized whereinthe arrangement of the multiple first and second openings, 62 and 64respectively, can be varied.

Each of the second openings 64 is spaced from between about 1 mm toabout 3.8 mm from the longitudinal central axis X₁-X₁ of each of thenozzles 44. Desirably, each of the second openings 64 is spaced frombetween about 1 mm to about 2.5 mm from the longitudinal central axisX-X of each of the nozzles 44.

Referring to FIGS. 2 and 4, each of the multiple second openings 64 canhave a stationary, elongated central pin or shaft 66 positioned therein.The elongated central pin 66 has a constant outer diameter d₄ and issecured to the spinnerette 42, see FIG. 2. The diameter d₄ of thecentral pin 66 can vary. Desirably, the diameter d₄ of the central pin66 is at least 0.25 mm. More desirably, the diameter d₄ of the centralpin 66 is at least 0.5 mm. Even more desirably, the diameter d₄ of thecentral pin 66 is at least 0.64 mm. Most desirably, the diameter d₄ ofthe central pin 66 is at least 0.75 mm.

Referring to FIG. 5, the stationary central pin 66 is shown beingpositioned parallel and adjacent to one of the hollow cylindrical tubes46. The pressurized gas 34 can follow a straight or a circuitous routethrough the second member or gas distribution plate 62 and the thirdmember or exterior plate 60 such that it will form an envelope, shroudor curtain of pressurized gas 34 around at least a portion of thecircumference of the hollow cylindrical tube 46. By “shrouding” it ismeant something that conceals, protects, or screens. In addition, thepressurized gas 34 existing through the adjacent second opening 64 willprovide a barrier or veil which will limit or prevent the heated aqueoussolution 20, extruded out of each of the nozzles 44, i.e. hollowcylindrical tubes 46, from contacting, touching and/or bonding to theheated aqueous solution 20 extruded from an adjacent nozzle 44. By“veil” it is meant something that conceals, separates, or screens like acurtain. In short, the pressurized gas 34 emitted through the multiplesecond openings 64 will form pressurized gas streams which will limit orprevent individual molten filaments from joining with one or more othermolten filaments and forming ropes and/or bundles. Desirably, thepressurized gas 34 can form an envelope, shroud or curtain around theentire circumference of each of the hollow cylindrical tubes 46. Thevelocity and pressure of the pressurized gas 34 can be varied to suitone's equipment.

Still referring to FIG. 5, one can clearly see that the hollowcylindrical tube 46 extends downward beyond the first opening 62 by avertical distance d₅ which is at least 1 mm. Desirably, the verticaldistance d₅ is at least 3 mm, and more desirably, the vertical distanced₅ is at least 5 mm.

In FIGS. 4 and 5, each of the multiple second openings 64 completelysurrounds the central pin 66 such that the pressurized gas 34 can beemitted about the entire outer circumference of each of the central pins66. One can view the pressurized gas 34 exited from each of the secondopenings 64 as shrouding or forming a veil about or around the heatedaqueous solution 20 extruded from each of the nozzles 44.

Referring now to FIGS. 6 and 7, the central pin 66 in each of the secondopenings 64 has a constant outer diameter d₄. In FIG. 6, the central pin66 is coaxially aligned within the second opening 64 such that asidewall 82 of the second opening 64 is aligned parallel to theelongated central pin 66. The sidewall 82 is also aligned perpendicularto the second opening 64. In this embodiment, an even discharge ofpressurized gas 34 is emitted about the entire circumference of thecentral pin 66. Alternatively, one can utilize a second opening 64′which has a venturi configuration, see FIG. 7. By “venturi” it is meanta constricted throat in a gas passage used to increase the velocity ofthe passing gas. Each of the multiple second openings 64′ has a sidewall84 which has a venturi shape. For example, the sidewall 84 has a convexshape which can form a restricted passageway about or below thecircumference of the central pin 66. The convex shape of the sidewall 84increases the velocity of the pressurized gas 34 passing therethrough.In some applications, this design may be desirable.

It should be noted that in FIG. 6, the terminal end of the central pin66 is flush with the outer surface of the exterior plate 60 while inFIG. 7, the terminal end of the central pin 66 is located inward fromthe outer surface of the exterior plate 60. Alternatively, the terminalend of the central pin 66 can be located within the thickness of theexterior plate 66.

Referring now to FIGS. 8-12, alternative embodiments for the firstopening 62 are depicted. In FIG. 8, a first opening 68 is shown having asquare configuration with a hollow cylindrical tube 46 positionedtherein. In FIG. 9, a first opening 70 is shown having a triangularconfiguration with a hollow cylindrical tube 46 positioned therein. InFIG. 10, a first opening 72 is shown having of two crescent shape slots74 spaced apart from a hollow cylindrical tube 46. In FIG. 11, a firstopening 76 is shown having four shorter crescent shape slots 78 spacedapart from a hollow cylindrical tube 46 and from one another. Lastly, inFIG. 12, a first opening 80 is shown having a plurality of circularholes 83 spaced apart from a hollow cylindrical tube 46. In FIG. 12, tencircular holes are shown each being equally spaced apart from oneanother. It should be understood by one skilled in the art that theactual number of holes 83 can vary. Likewise, various arrangements forthe first openings 62 can be utilized.

Referring to FIG. 13, an array 86 is shown which includes a plurality ofthe first openings 62, each having a nozzle 44 positioned therein, and aplurality of the second openings 64 formed in the third member orexterior plate 60. The array 86 has a longitudinal central axis X₁-X₁and a transverse central axis Y₁-Y₁. The array 86 includes a pluralityof columns 88 aligned parallel to the longitudinal central axis X₁-X₁and a plurality of rows 90 aligned parallel to the transverse centralaxis Y₁-Y₁. In the array 86, the number of columns 88 and the number ofrows 90 can each vary. The number of columns 88 can be greater than,equal to or less than the number of rows 90. Desirably, the number ofcolumns 88 exceeds the number of rows 90. The number of columns 88 canbe an even number or an odd number. Likewise, the number of rows 90 canbe an even number or an odd number. The number of columns 88 can rangefrom between about 1 per spinnerette to about 1,000 per spinnerette.Desirably, the number of columns 88 can range from between about 2 perspinnerette to about 800 per spinnerette. More desirably, the number ofcolumns 88 can range from between about 10 per spinnerette to about 500per spinnerette. Even more desirably, the number of columns 88 can rangefrom between about 20 per spinnerette to about 250 per spinnerette. InFIG. 13, the exterior plate 60 is shown with an even number of columns88 and an even number of rows 90.

The number of rows 90 can range from between about 1 per spinnerette toabout 100 per spinnerette. Desirably, the number of rows 90 can rangefrom between about 2 per spinnerette to about 50 per spinnerette. Moredesirably, the number of rows 90 can range from between about 3 perspinnerette to about 25 per spinnerette. Even more desirably, the numberof rows 90 can range from between about 6 per spinnerette to about 18per spinnerette. Most desirably, the exterior plate 60 will contain atleast about 10 rows 90 per spinnerette. In FIG. 13, eighteen rows 90 arepresent.

One will also notice that each of the nozzles 44, positioned in each ofthe columns 88, is offset or staggered from a nozzle 44 positioned in anadjacent column 88. By “staggered” it is meant to place on or as if onalternating sides of a centerline; set in a zigzag row or rows.Likewise, each of the nozzles 44, positioned in each of the rows 90, isoffset or staggered from a nozzle 44 positioned in an adjacent row 90.Desirably, at least one of the nozzles 44 in one of the columns or rows,88 or 90 respectively, is staggered from at least one of the nozzles 44present in an adjacent column or row, 88 or 90 respectively. Moredesirably, at least two of the nozzles 44 in one of the columns or rows,88 or 90 respectively, is staggered from at least two of the nozzles 44present in an adjacent column or row, 88 or 90 respectively. Even moredesirably, at least three of the nozzles 44 in one of the columns orrows, 88 or 90 respectively, is staggered from at least three of thenozzles 44 present in an adjacent column or row, 88 or 90 respectively.

It has been recognized that in order to achieve uniform and high qualityformation of the cellulose fibers 12, the nozzles 44 should be staggeredso that as the heated aqueous cellulose solution 20 is extruded intomultiple molten filaments, each of the multiple molten filaments canremain separate and distinct. By establishing a minimum distance betweentwo adjacent nozzles 44, the molten filaments extruded therefrom willnot touch or bond to one another. The staggering of the nozzles 44 alsominimizes the pressurized gas streams exiting from one of the nozzles 44from interfering with the pressurized gas streams associated with aneighboring nozzle 44.

Still referring to FIG. 13, the third member or exterior plate 60 has atleast about 8 of the first and second openings, 62 and 64 respectively,per linear centimeter. The number of first openings 62 can be equal toor be different from the number of second openings 64. The insidediameter d₂ of each of the first openings 62 can be equal to or bedifferent from the inside diameter d₃ of the second openings 64 or 64′.Desirably, the third member or exterior plate 60 has at least about 20of the first and second openings, 62 and 64 respectively, per linearcentimeter. More desirably, the a hollow cylindrical tube 46 exteriorplate 60 has at least about 40 of the first and second openings, 62 and64 respectively, per linear centimeter. Still more desirably, the thirdmember or exterior plate 60 has at least about 60 of the first andsecond openings, 62 and 64 respectively, per linear centimeter. Mostdesirably, the third member or exterior plate 60 has at least about 90of the first and second openings, 62 and 64 respectively, per linearcentimeter.

It should be apparent to one skilled in the art that many differentarrays can be constructed and utilized. For example, one could form anarray in the third member or exterior plate 60 that has at least sixrows 90 per spinnerette and each of the rows 90 includes an equal numberof the first and second openings, 62 and 64 respectively. Alternatively,one could form an array in the third member or exterior plate 60 thathas at least ten rows 90 per spinnerette and each of the rows 90includes at least two of the first openings 62, i.e. two of the nozzles44, and at least two of the second openings 68. Furthermore, one couldform an array in the third member or exterior plate 60 that has at leastten rows 90 per spinnerette and each of the rows 90 contains an unequalnumber of the first and second openings, 62 and 64 respectively.

Regardless of the particular array one selects, it should be noted thatby offsetting one of the first openings 62, with one of the nozzles 44located therein, in one of the columns 88 or rows 90, from one of thefirst openings 62 present in an adjacent column 88 or row 90, one canincrease the distance between adjacent first openings 62. Likewise, thedistance between two adjacent nozzles 44 is also increased. As thisdistance is increased, the likelihood that a molten filament extrudedfrom one of the nozzles 44 will contact or touch a molten filamentextruded from the adjacent nozzle 44 is decreased. Each of the firstopenings 62, in FIG. 13, is shown to contain a nozzle 44. By limiting orpreventing such contact, one can form individual molten filaments thatcan attenuate into very fine cellulose fibers. By “attenuate” it ismeant to make slender, fine, or small. Each of the molten filaments arethen coagulated, as well be explained later, to form a soft, solidcellulose fiber. By “coagulate” it is meant to cause a transformation ofa liquid into a soft, solid mass.

Referring now to FIG. 14, a second array 92 is shown which includes aplurality of the first openings 62 and a plurality of the secondopenings 64 formed in the third member or exterior plate 60. Each of thefirst openings 62 has a nozzle 44 positioned therein. The array 92 has alongitudinal central axis X₂-X₂ and a transverse central axis Y₂-Y₂. Thearray 92 includes a plurality of columns 94 aligned parallel to thelongitudinal central axis X₂-X₂ and a plurality of rows 96 alignedparallel to the transverse central axis Y₂-Y₂. In the array 92, thenumber of columns 94 and the number of rows 96 can each vary as wasexplained above with reference to FIG. 13. One noticeable difference,between the array 86, shown in FIG. 13, and the array 92, shown in FIG.14, is that in the array 92, every other column 94, as well as the twoouter rows 96, contains only the second openings 64. This creates apattern wherein each of the nozzles 44 is surrounded by eight of thesecond openings 64. This means that eight pressurized gas streams arepresent to separate and shroud each molten filament extruded from eachof the nozzles 44 from contacting or touching an adjacent moltenfilament. By keeping each molten filament separate, one can limit oreliminate roping and/or bundling of the molten filaments and therebyobtain multiple fine cellulose fibers.

Still referring to FIG. 14, one will also notice that the outer columns94, 94 on the left and right sides of the array 92 and the outer rows 96on the top and bottom of the array 92 are void of the first openings 62and the nozzles 44. This pattern is not required but can assist inlimiting air turbulence on each end of the array 92. In addition, onecan further limit air turbulence by making the two columns 94, 94,located on the right side of the Figure void of the first openings 62and the nozzles 44, as shown. Likewise, the outer two columns 94, 94 onthe left side of the array, as well as the outer two rows 96, 96 on thetop and bottom of the array 92 can also be made void of the firstopenings 62 and the nozzles 44.

Referring to FIGS. 15-18, four different arrays are depicted. In FIG.15, the third member or exterior plate 60 contains a plurality of firstand second openings, 62 and 64 respectively. In this array, each of thefirst openings 62 contains a nozzle 44 and each of the first openings 62is surrounded by three of the second openings 68 through whichpressurized gas is routed. This is referred to as a “three hole”pattern. In FIG. 16, the third member or exterior plate 60 contains aplurality of first and second openings, 62 and 64 respectively. In thisarray, each of the first openings 62 contains a nozzle 44 and each ofthe first openings 62 is surrounded by four of the second openings 64through which pressurized gas is routed. This is referred to as a “fourhole” pattern. In FIG. 17, the third member or exterior plate 60contains a plurality of first and second openings, 62 and 64respectively. In this array, each of the first openings 62 contains anozzle 44 and each of the first openings 62 is surrounded by six of thesecond openings 64 through which pressurized gas is routed. Each of thesecond openings 64 is spaced approximately 60 degrees apart from anadjacent second opening 62. This is referred to as a “six hole” pattern.In FIG. 18, the third member or exterior plate 60 contains a pluralityof first and second openings, 62 and 64 respectively. In this array,each of the first openings 62 contains a nozzle 44 and each of the firstopenings 62 is surrounded by eight of the second openings 64 throughwhich pressurized gas is routed. Each of the second openings 64 isspaced approximately 45 degrees apart from an adjacent second opening62. This is referred to as an “eight hole” pattern.

Referring to FIGS. 1, 13 and 19, the process 10 further includesdirecting the heated aqueous solution 20 through each of the nozzles 44formed in the first member or spinnerette 42. The first member orspinnerette 42 has multiple rows 90 of the first openings 62 eachcontaining one of the nozzles 44. The first member or spinnerette 42also has a plurality of second openings 64 formed therein. The firstopenings 62 differ from the second openings 64 in that each of the firstopenings 62 has a nozzle 44 positioned therein. In the first member orspinnerette 42, at least one of the nozzles 44, located in a row 90, isstaggered from at least one of the nozzles 44 located in an adjacent row90. Each of the nozzles 44 is concentrically arranged within each of thefirst openings 62 and one or more of the second openings 64 are locatedadjacent to each of the nozzles 44.

The heated aqueous solution 20 is extruded through the hollowcylindrical tube 46 of each of the nozzles 44 at a predetermined backpressure. The back pressure should be at least 10 bar to form a moltenfilament 98. The back pressure can range from between about 10 bar toabout 200 bar as was explained earlier. The velocity of the heatedaqueous solution 20 exiting the nozzle 44, including the adjacent airstream, should be at least about 100 meters per second. Desirably, thevelocity of the heated aqueous solution 20 exiting the nozzle 44,including the adjacent air stream, should be at least about 250 metersper second. More desirably, the velocity of the heated aqueous solution20 exiting the nozzle 44 should be at least about 450 meters per second.The extruded molten filament 98 forms a bulge 100, see FIG. 19,immediately upon exiting the hollow cylindrical tube 46. A number offactors contribute to this bulge 100 being formed. Such factors includebut are not limited to: friction between the aqueous solution 20 and theinside diameter d of the hollow cylindrical tube 46, the velocity of theaqueous solution 20, the viscosity of the aqueous solution 20, theinside diameter d of the hollow cylindrical tube 46, gravity acting onthe aqueous solution 20, etc.

The extruded molten filament 98 is at least partially shrouded, anddesirably, completely shrouded, by the pressurized gas 34 emittedthrough the first opening 62 which surrounds each of the nozzles 44. Thepressurized gas 34 can be heated to a temperature of at least about 100°C. Desirably, the pressurized gas 34 is heated to a temperature of atleast about 120° C. More desirably, the pressurized gas 34 is heated tothe same temperature as that of the heated aqueous solution 20. Thepressurized gas 34 is emitted as gas streams 102 aligned essentiallyparallel to the molten filament 98. The pressurized gas streams 102 forma veil or curtain around at least a portion of the circumference of themolten filament 98. Desirably, the pressurized gas streams 102 form aveil or curtain around the entire circumference of the molten filament98. The pressurized gas 34, which is desirably air, is emitted from eachof the first openings 62 at a velocity of at least 45 meters per secondas was explained earlier. The pressurized gas streams 102, along withgravity, will attenuate and accelerate each of the molten filaments 98into a circular cross-sectional configuration having a diameter of lessthan about 15 microns. Desirably, each of the molten filaments 98 willhave a diameter of from between about 0.5 microns to about 10 microns.More desirably, each of the molten filaments 98 will have a diameter offrom between about 1 micron to about 8 microns. Still more desirably,each of the molten filaments 98 will have a diameter of from betweenabout 1 micron to about 5 microns. Most desirably, each of the moltenfilaments 98 will have a diameter of from between about 1 micron toabout 3 microns.

Still referring to FIG. 19, the attenuation and acceleration will occurover a predetermined distance h. The actual amount of attenuation andthe acceleration can vary. Both the amount of attenuation and theacceleration can be calculated and can be adjusted to obtain a cellulosefiber 12 having a predetermined diameter. The distance h can varydepending upon a number of factors, including but not limited to: thecomposition of the heated aqueous solution 20, the finish diameter ofthe cellulose fibers, the temperature of the molten filament 98, theinside diameter of the hollow cylindrical tube 46, etc. The distance hcan range from between about 3 centimeters to about 3 meters. Desirably,the distance h should range from between about 15 centimeters to about 2meters. More desirably, the distance h should range from between about20 centimeters to about 1.5 meters. Even more desirably, the distance hshould range from between about 30 centimeters to about 1 meter.

The process 10 further includes extruding the heated aqueous solution 20downward from each of the nozzles 44 parallel to a longitudinal centralaxis X₃-X₃ and contacting each of the molten filaments 98 with a liquid104. The liquid 104 causes each of the molten filaments 98 to coagulateinto a continuous solid fiber 12. The liquid 104 can be water, alcoholor a solution having a high concentration of water. The temperature ofthe liquid 104 can be adjusted to suit one's particular needs. Forexample, the liquid 104 can be at room temperature. Alternative, theliquid 104 could be cooler than room temperature. The velocity of theliquid 104 can also vary. It has been found in some applications thatusing a pressurized liquid 104 produces a better chemical reactionbetween the molten filaments 98 and the liquid 104. For example, theliquid 104 can be introduced as a hydro jet. By “hydro jet” it is meanta jet of pressurized liquid or mixture of liquid and air. The liquid 104causes a major portion of the solvent 18 to solvate into the liquidsolution and thus allow the molten filaments 98 to transform orcoagulate into a continuous solid fiber. The amount of solvent 18 thatis actually removed by the liquid 104 can vary depending upon thepercentage of solvent 18 present in the heated aqueous solution 20.Desirably, at least 75% of the solvent present in the heated aqueoussolution 20 will be removed. More desirably, at least about 80% of thesolvent present in the heated aqueous solution 20 will be removed. Evenmore desirably, at least about 85% of the solvent present in the heatedaqueous solution 20 will be removed. Most desirably, at least about 90%of the solvent present in the heated aqueous solution 20 will beremoved.

For example, if the heated aqueous solution 20, as it leaves the nozzle44, includes about 85% solvent, about 10% cellulose and about 5% water,then once the molten filament 98 is contacted with the liquid 104, thepercentages can change to about 10% solvent, about 10% cellulose andabout 80% water. In order to remove all of the solvent 18 that ispresent in each of the molten filaments 98, one will normally have tosubject the cellulose fibers 12 to additional washing steps.

Each of the molten filaments 98 should be contacted with the liquid 104at a distance h of at least about 3 centimeters from each of the nozzles44. The liquid 104 can be introduced at an angle alpha α. The angle αcan range from between about 5 degrees to about 175 degrees as measuredfrom the longitudinal central axis X₃-X₃. Desirably, the angle α canrange from between about 10 degrees to about 135 degrees as measuredfrom the longitudinal central axis X₃-X₃. More desirably, the angle αcan range from between about 25 degrees to about 90 degrees as measuredfrom the longitudinal central axis X₃-X₃. Even more desirably, the angleα can range from between about 30 degrees to about 60 degrees asmeasured from the longitudinal central axis X₃-X₃. The angle α can be anacute angle or an obtuse angle as measured from the hollow, cylindricaltube 46.

Referring again to FIGS. 2 and 19, as each of the molten filaments 98 isextruded from each of the hollow cylindrical tubes 46 and each isattenuated and accelerated by the pressurized gas 34 exiting through thefirst openings 62 as the pressurized gas streams 102. Additionalpressurized gas 34 is emitted from each of the second openings 64. Thepressurized gas emitted from each of the second openings 64 limits orprevents each of the molten filaments 98 from physically contacting oneanother. This decreases the possibility that two or more of the moltenfilaments 98 can contact or touch one another and form ropes and/orbundles of filaments 98. It is desirable that each of the moltenfilaments 98 be kept separate and distinct from adjacent moltenfilaments 98. By doing so, one can produce a multitude of individualcellulose fibers 12 each having essentially the same diameter.

The pressurized gas 34 emitted through each of the second openings 64will shroud or assist in keeping adjacent molten filaments 98 separatefrom one another. The pressurized gas 34 emitted from each of the secondopenings 64 can also be heated so that it has an elevated temperature.The temperature of the pressurized gas 34 emitted from each of thesecond openings 64 can be equal to or closely match the temperature ofthe pressurized gas streams 102. Alternatively, the temperature of thepressurized gas 34 emitted from each of the second openings 64 can be ata higher or a lower temperature than the temperature of the pressurizedgas streams 102.

Likewise, the velocity of the pressurized gas 34 emitted from each ofthe second openings 64 can be adjusted to be less than, equal to or begreater than the velocity of the pressurized gas streams 102. Desirably,the velocity of the pressurized gas 34 emitted from each of the secondopenings 64 is essentially equal to the velocity of the pressurized gasstreams 102. Furthermore, the velocity of the pressurized gas 34 emittedfrom each of the first and second openings, 62 and 64 respectively, canbe less than, equal to or greater than the velocity of the heatedaqueous solution 20 extruded from each of the nozzles 44. Desirably, thevelocity of the pressurized gas 34 emitted from each of the first andsecond openings, 62 and 64 respectively, is greater than the velocity ofthe heated aqueous solution 20 extruded from each of the nozzles 44.

Still referring to FIGS. 1 and 19, the continuous cellulose fibers 12are still relatively soft and wet when they are collected on a movingsurface 106. The moving surface 106 can be a conveyor belt 108, asillustrated, or be some other type of moving member, such as a rotatabledrum. The moving surface 106, i.e. the conveyor belt 108 or therotatable drum, can be porous so that water can easily passtherethrough. The moving surface 106 can be constructed so as to be ableto move at different speeds. As the continuous, coagulated cellulosefibers 12 contact the moving surface 106 they will accumulate to form anon-woven web 110. The loft or thickness t of the non-woven web 110, seeFIG. 19, will vary depending upon the speed of the moving surface 106.For example, the slower the speed of the moving surface 106, the greaterthe loft or thickness t of the non-woven web 110 will be. Likewise, asthe speed of the moving surface 106 is increased, the loft or thicknessof the non-woven web 110 will decrease.

The distance between the nozzles 44 and the moving surface 106 iscommonly referred to in the industry as the “die to collector” distance.This distance, denoted h₁ in FIG. 19, can range from between about 15centimeters to about 3 meters. Desirably, the distance h₁ is frombetween about 20 centimeters to about 1 meter. More desirably, thedistance h₁ is from between about 25 centimeters to about 120centimeters. Even more desirably, the distance h₁ is from between about30 centimeters to about 90 centimeters. Most desirably, the distance h₁is at least 50 centimeters.

The non-woven web 110 can be constructed to have an open pore structure.The size and quantity of the pores can vary. The non-woven web 110 canbe an entangled accumulation of the coagulated cellulose fibers 12. By“non-woven” it is meant that the fibers 12 are not arranged or weavedinto a set pattern. The non-woven web 110 can be constructed of 100%cellulose fibers 12 or be a combination of cellulose fibers 12 andpolymers fibers. The polymers fibers (not shown) can be extruded fromanother extruder which is positioned upstream or downstream from the dieblock/spinnerette assembly 26, see FIG. 1. The polymers fibers can bepolyolefin fibers, such as polyethylene and polypropylene fibers, orthey can be bicomponent fibers, etc. The percentage of the variouscellulose and polymer fibers can vary to suit one's particular needs andrequirements.

It should be understood that the cellulose fibers 12 can be combinedwith a polymer to form a bicomponent fiber as well.

The process 10 can be started up by heating the aqueous solution 20 to apredetermined temperature. The aqueous solution 20 can be heated to anelevated temperature of from between about 80° C. to about 140° C.Desirably, the aqueous solution 20 is heated to a temperature of atleast 100° C. More desirably, the aqueous solution 20 is heated to atemperature of at least about 110° C. Even more desirably, the aqueoussolution 20 is heated to a temperature of about 120° C. Simultaneouslyor sequentially, the pressurized gas 34 can be heated to an elevatedtemperature. The elevated temperature can be at least 100° C. or higher.Desirably, the elevated temperature of the pressurized gas 34 is about110° C. More desirably, the elevated temperature of the pressurized gas34 is about 120° C. The heated aqueous solution 20 is then directedthrough the die block/spinnerette assembly 26 to the first member orspinnerette 42. At the first member or spinnerette 42, the heatedaqueous solution 20 is extruded through each of the multitude of thehollow cylindrical tubes 46 which form the nozzles 44. The heatedaqueous solution 20 is extruded through each of the hollow cylindricaltubes 46 at a back pressure of from between about 5 bar to about 200bar. Desirably, the back pressure is higher than 20 bar. More desirably,the back pressure is higher than 30 bar. Even more desirably, the backpressure is higher than 40 bar. The heated pressurized gas 34 issimultaneously routed through each of the first and second openings, 62and 64 respectively, at a velocity of from between about 1 meter persecond to about 10 meters per second. The velocity of the heatedpressurized gas 34 is then gradually increased until the pressurized gas34 reaches a velocity of at least about 45 meters per second. At thistime, production grade cellulose fibers 12 can be extruded.

Shutting down the process 10 can be accomplished by turning off the heatused to heat the pressurized gas 34. The velocity of the pressurized gas34 is then gradually reduced from about 45 meters per second down to 0meters per second. The flow of the heated aqueous solution 20 flowingthrough each of the nozzles 44 is then stopped. The heated aqueoussolution 20 is then allowed to cool down to room temperature. At thistime the various lines or hoses which route the heated aqueous solution20 to the die block/spinnerette assembly 26 can be flushed or purged. Itis important to flush or purge such lines or hoses, especially if thedope delivery mechanism 24 is to be inoperative for an extended periodof time.

Referring to FIG. 20, a coagulated cellulose fiber 12 is shown having acircular cross-sectional configuration with a diameter d₆. The diameterd₆ of the cellulose fiber 12 should be less than about 15 microns.Desirably, the diameter d₆ of the cellulose fiber 12 is less than about10 microns. More desirably, the diameter d₆ of the cellulose fiber 12ranges from between about 0.5 microns to about 8 microns. Even moredesirably, the diameter d₆ of the cellulose fiber 12 ranges from betweenabout 0.5 microns to about 5 micron. Most desirably, the diameter d₆ ofthe cellulose fiber 12 ranges from between about 0.5 microns to about 4microns.

The cellulose fiber 12 has a uniformly smooth outer surface 112 whenviewed at a magnification of 100×. The coagulated cellulose fiber 12,before contacting the moving surface 106, contains less than about 20%of the water soluble solvent 18. In other words, the concentration ofthe solvent 18 is measured immediately after the molten filament 98 iscoagulated into a solid fiber 12. Desirably, the coagulated cellulosefiber 12, before contacting the moving surface 106, contains less thanabout 15% of the water soluble solvent 18. More desirably, thecoagulated cellulose fiber 12, before contacting the moving surface 106,contains less than about 10% of the water soluble solvent 18. Even moredesirably, the coagulated cellulose fiber 12, before contacting themoving surface 106, contains less than about 8% of the water solublesolvent 18.

As mentioned above, each of the cellulose fibers 12 is formed from aheated aqueous solution 20 that can vary in composition. The aqueoussolution 20 can include from between about 5% to about 35% cellulose,from about 60% to 90% solvent 18, and from between about 5% to about 35%water. Typically, the aqueous solution will contains about 10%cellulose, about 85% solvent and about 5% water. The most common watersoluble solvent 18 is N-methyl-morpholine-N-oxide (NMMO).

The heated aqueous solution 20 is extruded through the first member orspinnerette 42 at a throughput of greater than 0.1 grams/hole/minute ata production speed of up to 750 meters per minute. Desirably, the heatedaqueous solution 20 is extruded through the first member or spinnerette42 at a throughput of greater than 0.5 grams/hole/minute at a productionspeed of up to 750 meters per minute. More desirably, the heated aqueoussolution 20 is extruded through the first member or spinnerette 42 at athroughput of greater than 1 gram/hole/minute at a production speed ofup to 750 meters per minute. Immediately after being extruded from eachof the nozzles 44, the heated aqueous solution 20 is formed into amolten filament 98. The molten filament 98 is attenuated and acceleratedby gravity and by the adjacent pressurized gas streams 102 exiting fromthe first openings 62. Each of the molten filaments 98 are coagulated bythe liquid 104 into a continuous, solid fiber 12. This solid fiber 12 isstill soft and wet and contains less than 20% of the water solublesolvent 18.

Referring again to FIG. 1, the multiple continuous cellulose fibers 12are collected on the moving surface 106 to form the non-woven celluloseweb 110. The non-woven cellulose 110 web contains less than about 20%solvent. The non-woven cellulose web 110 has a basis weight of at leastabout 1 gram per square meter (gsm). Alternatively, the non-wovencellulose web 110 has a basis weight of at least about 1.25 gsm. Stillalternatively, the non-woven cellulose web 110 has a basis weight of atleast about 1.5 gsm or higher.

The non-woven cellulose web 110 is directed to a wash station 114 wherean additional liquid, desirably in the form of water, is brought intocontact with the non-woven cellulose web 110. This additional liquidmixes with the residual solvent 18 and reduces the concentration of thesolvent 18 to less than 10%. Desirably, the concentration of the solvent18 in the cellulose fiber 12 is reduced to less than 5%. More desirably,the concentration of the solvent 18 in the cellulose fiber 12 is reducedto less than 3%. Even more desirably, the concentration of the solvent18 in the cellulose fiber 12 is reduced to less than 1%.

It should be noted that the non-woven cellulose web 110 can be subjectedto additional washing stations so that over 99% of the solvent 18 isremoved.

After the concentration of the solvent 18 has been reduced to apreselected value or until essentially all of the solvent 18 is removedfrom the non-woven cellulose web 110, the non-woven web 110 is dried ina dryer 116. The non-woven cellulose web 110 can be dried using heatedair, steam, moving air, contact with another member such as a felt or acloth, etc. Other means of drying the non-woven cellulose web 110 thatare known to those skilled in the art can also be used.

Each of the cellulose fibers 12 is white or off white in color. Acolorant can be added to the heated aqueous solution 20 or to the moltenfilaments 98 to form cellulose fibers 12 of a particular color, ifdesired.

The dried non-woven cellulose web 110 can be subjected to othermechanical methods, if desired. For example, the non-woven cellulose web110 can be hydroentangled. Furthermore, the non-woven cellulose web 110can be subjected to any paper making procedure, including but notlimited to: being perforated, being punched, being stamped, beingembossed, being printed, being coated, etc. After being so treated, thenon-woven cellulose web 110 can be wound up into a supply roll 118. Thesupply roll 118 can be loaded and transported in a semi-trailer or in arailroad car to a manufacturer, distributor or consumer, or the supplyroll 118 can be stored until it is ready to be shipped to a consumer.

While the invention has been described in conjunction with severalspecific embodiments, it is to be understood that many alternatives,modifications and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, this inventionis intended to embrace all such alternatives, modifications andvariations which fall within the spirit and scope of the appendedclaims.

1. An apparatus for extruding cellulose fibers, comprising: a) a firstmember having multiple nozzles arranged in rows, each of said nozzleshaving an inside diameter through which an aqueous solution comprised ofcellulose and a solvent can be extruded, and having at least one passageformed therein through which a pressurized gas can be routed; b) asecond member secured to said first member, said second member havingmultiple corridors formed therethrough which are connected to said atleast one passage formed in said first member, and multiple openingsformed therein through which said multiple nozzles can pass; and c) athird member secured to said second member, said third member havingmultiple first openings formed therethrough, each of said multiple firstopenings sized to permit one of said multiple nozzles to pass through,each of said multiple first openings being concentrically aligned abouteach of said multiple nozzles, each of said multiple first openingsbeing connected to said pressurized gas corridors formed in said secondmember and each capable of emitting pressurized gas therethrough suchthat said pressurized gas at least partially surrounds said aqueoussolution extruded from each of said multiple nozzles, and said thirdmember also having multiple second openings formed therethrough whichare connected to said pressurized gas corridors formed in said secondmember, each of said multiple second openings being positioned adjacentto one of said multiple nozzles in each of said rows, and each of saidmultiple second openings having a diameter through which saidpressurized gas can be emitted.
 2. The apparatus of claim 1 capable offorming cellulose fibers having a diameter of less than about 15 micronsat a throughput of greater than 0.1 grams/hole/minute.
 3. The apparatusof claim 1 capable of forming cellulose fibers having a diameter of lessthan about 5 microns at a throughput of greater than 0.5grams/hole/minute.
 4. The apparatus of claim 1 wherein said third memberhas an even number of rows of nozzles with at least one of said nozzlesin one row being offset from one of said nozzles in an adjacent row. 5.The apparatus of claim 1 wherein each of said multiple hollowcylindrical tubes has an inside diameter ranging from between about0.125 millimeters to about 01.25 millimeters.
 6. The apparatus of claim1 wherein each of said multiple nozzles is formed from stainless steel.7. The apparatus of claim 1 wherein each of said multiple secondopenings has a venturi formed therein.
 8. The apparatus of claim 1wherein said third member has an odd number of rows, and wherein atleast two of said nozzles in one row are offset from two of said nozzlesin an adjacent row.
 9. The apparatus of claim 1 wherein each of saidsecond openings contains a pin therein.
 10. An apparatus for extrudingcellulose fibers, comprising: a) a filter block secured to a dopedelivery mechanism, said filter block having a first passageway formedtherein through which an aqueous solution comprised of cellulose and asolvent can be routed, and a second passageway formed therein throughwhich a pressurized gas can be routed; b) a spinnerette secured to saidfilter block, said spinnerette having multiple nozzles arranged in rows,each of said nozzles having a longitudinal central axis with an insidediameter through which said aqueous solution can be extruded, and saidspinnerette having at least one passage formed therethrough which isconnected to said second passageway; c) a gas distribution plate securedto said spinnerette, said gas distribution plate having multiplecorridors formed therethrough which are connected to said at least onepassage formed in said spinnerette, and multiple openings formed thereinthrough which said multiple nozzles can pass; and d) an exterior platesecured to said gas distribution plate, said exterior plate havingmultiple first openings formed therethrough, each of said multiple firstopenings sized to permit one of said multiple nozzles to pass through,each of said multiple first openings being concentrically aligned abouteach of said multiple nozzles, each of said multiple first openingsbeing connected to said pressurized gas corridors formed in said gasdistribution plate and each capable of emitting pressurized gastherethrough such that said pressurized gas at least partially surroundssaid aqueous solution extruded from each of said multiple nozzles, andsaid exterior plate also having multiple second openings formedtherethrough which are connected to said pressurized gas corridorsformed in said gas distribution plate, each of said multiple secondopenings being positioned adjacent to one of said multiple nozzles ineach of said rows, at least one of said nozzles being offset from anozzle in an adjacent row, and each of said multiple second openingshaving a diameter through which said pressurized gas can be emitted. 11.The apparatus of claim 10 capable of forming cellulose fibers having adiameter of less than about 15 microns at a throughput of greater than0.1 grams/hole/minute.
 12. The apparatus of claim 10 capable of formingcellulose fibers having a diameter of less than about 5 microns at athroughput of greater than 0.5 grams/hole/minute.
 13. The apparatus ofclaim 10 wherein said exterior plate has at least three rows of nozzleswith each row containing an equal number of said first and secondopenings.
 14. The apparatus of claim 10 wherein said exterior plate hasat least three rows of nozzles with each row containing an unequalnumber of said first and second openings.
 15. The apparatus of claim 10wherein said exterior plate has at least 20 openings per linearcentimeter.
 16. An apparatus for extruding cellulose fibers, comprising:a) a dope delivery mechanism having a first conduit formed thereinthrough which an aqueous solution comprised of cellulose and a solventcan be routed, and a second conduit formed therein through which apressurized gas can be routed; b) a filter block secured to said dopedelivery mechanism, said filter block having at least two separatepassageways formed therethrough, each of said passageways connectingwith one of first and second conduits; c) a spinnerette secured to saidfilter block, said spinnerette having multiple nozzles arranged in rows,each of said nozzles being an elongated, hollow tube having alongitudinal central axis with a cross-section having an opening throughwhich said aqueous solution can be extruded and having at least onepassage formed therein which is connected to said pressurized gaspassageway formed in said filter block; d) a gas distribution platesecured to said spinnerette, said gas distribution plate having multiplecorridors formed therein which are connected to said passage formed insaid spinnerette for routing said pressurized gas therethrough, andmultiple openings formed therethrough each of which is sized to permitone of said multiple nozzles to pass through; and e) an exterior platesecured to said gas distribution plate, said exterior plate havingmultiple first openings formed therethrough, each of said multiple firstopenings sized to permit one of said multiple nozzles to pass through,each of said multiple first openings being concentrically aligned abouteach of said multiple nozzles, each of said multiple first openingsbeing connected to said pressurized gas corridors formed in said gasdistribution plate and each capable of emitting pressurized gastherethrough such that said pressurized gas at least partially surroundssaid aqueous solution extruded from each of said multiple nozzles, andsaid exterior plate also having multiple second openings formedtherethrough which are connected to said pressurized gas corridorsformed in said gas distribution plate, each of said multiple secondopenings having a central shaft positioned therein and having across-section through which said pressurized gas can be emitted, and atleast one of said nozzles in one of each of said rows being staggeredfrom at least one of said nozzles in an adjacent row.
 17. The apparatusof claim 16 wherein pressurized gas can pass through said assembly at avelocity of at least 45 meters per second and each of said multiplefirst openings includes at least two crescent shaped slots.
 18. Theapparatus of claim 16 wherein said exterior plate has at least 60openings per linear centimeter.
 19. The apparatus of claim 16 whereinsaid exterior plate has an even number of rows of nozzles with at leastthree of said nozzles in one row being offset from three of said nozzlesin an adjacent row.
 20. The apparatus of claim 16 wherein said exteriorplate has an odd number of rows of nozzles with at least three of saidnozzles in one row being offset from three of said nozzles in anadjacent row.